1. Technical Field
The present disclosure relates to a conductive film and a touch panel which are capable of improving visibility.
2. Related Art
As recent touch panels, capacitive touch panels have become mainstream. Transparent touch panels which have a mesh-like pattern formed thereon using copper or silver as a low resistive element to obtain the same sensitivity as that of a small touch panel (with a size of 5 to 8 inches) and which have excellent sensitivity and permeability have been mass-produced as large touch panels with a size of 10 to 15 inches.
A touch panel having a two-layered structure in which a pattern for a sensor is formed on the front surface of a base material and a pattern for driving is formed on the back surface of the base material is commonly known. A one-layer type pattern obtained by forming drive and sensor patterns on one surface of a base material has also been devised. With this pattern, the production process of a sensor can be simplified and the sensor can be produced at low cost.
The use of a coordinate detection IC corresponding to such a pattern makes it possible to provide a low-cost touch sensor which has a configuration in which an antenna pattern can be disposed on an opposite side of a one-layer type electrostatic touch panel and which has a touch sensor function as well as an antenna function. Additionally, by incorporating the antenna pattern into the touch panel, the space for a near field communication antenna reading unit and a Bluetooth antenna unit, which are conventionally provided as external units, can be saved, and thus a smaller device can be provided.
A conductive film having a configuration in which an antenna pattern is formed on a plastic film, such as a polyester film, is known as a conductive film used for a touch panel or the like.
There is a demand from customers to suppress the impedance of the antenna pattern in such a conductive film. For example, Japanese Patent No. 5321151 discloses a conductive film in which the width, thickness, and the like of a conductive mesh are specified and an excellent surface resistance value and an excellent transmittivity can be obtained even when the thickness is small.
However, the conductive film disclosed in Japanese Patent No. 5321151 is not intended to obtain excellent visibility, and it is not clear that the visibility is excellent.
In order to reduce the impedance of the antenna pattern, for example, it is possible to employ a method of increasing a pattern sectional area by increasing a pattern width. However, an increase in pattern width causes a problem that the visibility of the touch panel deteriorates. When the pattern width is increased, the antenna pattern can be observed with the naked eyes, which leads to a deterioration in the visibility with respect to an image display or the like on a display.